Vitamin B12, or Cobalamin, is required for the synthesis of DNA. When deficient, an imbalance occurs between the growth of the nucleus and the rest of the cell, resulting in large megaloblastic cells. The cells produced are large and fragile, leading to shape abnormalities and fragmentocytes, especially in the red image.

In this patient, vitamin B12 was 50 pmol/L, hemoglobin , MCV 101 fmol and RDW . As the fragile cells disintegrated, the LDH was also elevated by . Vitamin B12 deficiency in this case was caused by antibodies to intrinsic factor.